Ozone direct oxidation pretreatment and catalytic oxidation post-treatment coupled with ABMBR for landfill leachate treatment

Simultaneous Emerging Contaminant Removal and H2O2 Generation Through Electron Transfer Carrier Effect of Bi─O─Ce Bond Bridge Without External Energy Consumption

Conventional advanced oxidation processes (AOPs) require significant external energy consumption to eliminate emerging contaminants (ECs) with stable structures. Herein, a catalyst consisting of nanocube BiCeO particles (BCO-NCs) prepared by an impregnation-hydrothermal process is reported for the first time, which is used for removing ECs without light/electricity or any other external energy input in water and simultaneous in situ generation of H2O2. A series of characterizations and experiments reveal that dual reaction centers (DRC) which are similar to the valence band/conducting band structure are formed on the surface of BCO-NCs. Under natural conditions without any external energy consumption, the BCO-NCs self-purification system can remove more than 80% of ECs within 30 min, and complete removal of ECs within 30 min in the presence of abundant electron acceptors, the corresponding second-order kinetic constant is increased to 3.62 times. It is found that O2 can capture electrons from ECs through the Bi─O─Ce bond bridge during the reaction process, leading to the in situ production of H2O2. This work will be a key advance in reducing energy consumption for deep wastewater treatment and generating important chemical raw materials.

Recent progress and perspectives of typical renewable bio-based flocculants: characteristics and application in wastewater treatment

The research on bio-based flocculants for waste resource utilization and environmental protection has garnered significant attention. Bio-based flocculants encompass plant-based, animal-based, and microbial variants that are prepared and modified through biological, chemical, and physical methods. These flocculants possess abundant functional groups, unique structures, and distinctive characteristics. This review comprehensively discussed the removal rates of conventional pollutants and emerging pollutants by bio-based flocculants, the interaction between these flocculants and pollutants, their impact on flocculation performance in wastewater treatment, as well as their application cost. Furthermore, it described the common challenges faced by bio-based flocculants in practical applications along with various improvement strategies to address them. With their safety profile, environmental friendliness, efficiency, renewability, and wide availability from diverse sources, bio-based flocculants hold great potential for widespread use in wastewater treatment.

The efficiency and mechanism of excess sludge-based biochar catalyst in catalytic ozonation of landfill leachate

In this study, biochar was produced based on dehydrated excess sludge from the municipal wastewater treatment plant, which was used for catalytic ozonation of pollutants derived from landfill leachate. The necessary catalytic sites in the structure of biochar were originated from the inorganic metals and organic matters in the sludge, which included a large number of functional groups (e.g., C-C, CO, etc.), adsorbed oxygen (Oads accounted for 44.82%) and electron defects (ID/IG=1.01). These active sites could promote the generation of reactive oxygen species (ROS) (e.g., ·OH,·O2-, etc.). The synergistic interaction between the microorganisms in the activated sludge also facilitated the removal rates of pollutants. Proteobacteria, Bacteroidetes, and Deinococcu-Thermus were crucial in the bioreactor. In 16 days of reaction, the removal ratios of NH+4-N and COD were 98.95 ± 0.11% and 90.89 ± 0.47%, respectively. This study not only explains the mechanism of catalytic ozonation of biochar, but also provides a new way of the practical treatment of landfill leachate.

Construction of triphase interface for catalytic ozonation of polluted water

The utilization efficiency of ozone determines the cost of catalytic ozonation in water treatment. Herein, a triphase catalytic system was constructed by aerating ozone through a CeO2 loaded Al2O3 ceramic membrane (CeO2-CM) for disinfection and antibiotic degradation. Ozone aeration and a packed catalyst system (CeO2-Packing) were set as the controls. Results showed that CeO2-CM reduced the ozone escape by 34.6%-56.2%. The ozone utilization capacity of CeO2-CM for E. coli inactivation was 33.1% and 33.8% higher than those of CeO2-Packing and ozone aeration, respectively. The ozone utilization capacity of CeO2-CM for sulfamethoxazole degradation was 88.5% and 183.1% higher than those of CeO2-Packing and ozone aeration, respectively. CeO2-CM, with the lowest ozone escape and highest ozone utilization efficiency, significantly enhanced the performance of catalytic ozonation in disinfection and antibiotic degradation. This work proposes a feasible strategy for minimizing ozone consumption in water treatment.

Simultaneous removal of organics and ammonia using a novel composite magnetic anode in the electro-hybrid ozonation-coagulation (E-HOC) process toward leachate treatment

To achieve simultaneous organics and ammonia (NH₄⁺-N) removal toward leachate treatment, this study designed a composite anode (CA⁺), in which iron powders were attracted to RuO₂-IrO₂/Ti tube surface by an inserted magnet and utilized in electro-hybrid ozonation-coagulation (E-HOC). The E-HOC (CA⁺) resulted in higher chemical oxygen demand (COD) and NH₄⁺-N removal with most content of CO₂/H₂O and gaseous N in product compared with E-HOC (Fe⁺), electrolysis ozonation and single ozonation. Reactive chlorine species (RCS) and coagulants were co-produced by compositing RuO₂-IrO₂/Ti and Fe powders, resulting in multiple reactions including electrocoagulation, ozone oxidation, synergistic between ozone and coagulants (SOC), electrolytic chloride and synergistic oxidation between active chlorine and ozone (SCO) occurred. Hydroxyl radical (•OH) generated through SOC reaction was promoted due the RCS generation in E-HOC. The interaction between •OH and Cl^-/ClO^- also contributed to enhanced Cl•/ClO• production. Consequently, synergy of chlorine, coagulants and ozone enhanced reactive species generation which contributed to favorable organics and NH₄⁺-N removal. Enhanced •OH and RCS are also attributed to conversion of bio-refractory organics like polyphenol, polycyclic aromatics and S-containing to biodegradable ones, e.g., aliphatic compounds and CHO. This study provides an easily operating strategy for leachate treatment with high content organics and NH₄⁺-N.

Electro-dissolved ozone flotation (E-DOF) integrated anoxic/oxic membrane reactor for leachate treatment from a waste transfer station

With high organics and ammonia, leachate from waste transfer stations (WTSs) is among the most complex wastewater that cannot be easily disposed by signal biological processes. In this study, an electro-dissolved ozone flotation (E-DOF) was established, in which dissolved ozone flotation (DOF) and electro-coagulation (EC) occurred concurrently in one unit and integrated with anoxic/oxic membrane bioreactor (A/O-MBR) to dispose leachate from a WTS. In the integrated reactor, E-DOF acted as pretreatment and advanced treatment unit. A/O-MBR acted as secondary treatment unit. The E-DOF pretreatment achieved 34.48% COD and 16.96% NH3-N removal efficiency through synergistic effect between EC and DOF. BOD5/COD of leachate was increased from 0.32 to 0.51 after E-DOF pretreatment, indicating the enhancement of biodegradability. Molecular weight distribution (MWD) and three-dimensional excitation-emission matrix (3D-EEM) analysis demonstrate that the reduction of molecular weight and elimination of refractory organics through EC, ozone, and their interacted product (•OH) are attributed to biodegradability enhancement in lechate. Microbial community analysis proved that chemoheterotrophy and oxic chemoheterotrophy functions, mainly provided by Truepera, Aquamicrobium, Saprospiraceae, and Lentimicrobiaceae, ensured the efficient degradation of organic in the secondary processes. E-DOF advanced treatment effectively disposed residual contaminant in MBR effluent. The E-DOF advanced treatment mainly disposed residual contaminant in MBR effluent. High removal efficiency of COD (98.59 ± 0.27%), NH3-N (95.59 ± 0.50%), TN (95.37 ± 0.73%), and TP (96.75 ± 1.66%) were observed in the integrated reactor, and final effluent met the discharge standards for inclusion in the sewage pipe network in China.

Advanced treatment of landfill leachate through combined Anammox-based biotreatment, O3/H2O2 oxidation, and activated carbon adsorption: technical performance, surrogate-based control strategy, and operational cost analysis

The complexity of landfill leachate makes it difficult to treat it with a single biological/ physical/chemical process. Moreover, the dynamic leachate characteristics pose a challenge for effective process control. Therefore, a combined treatment, consisting of a one-stage partial nitrification-Anammox process, an O₃/H₂O₂ process, and a granular activated carbon filtration (GAC) process, was investigated. Meanwhile, a novel surrogate-based ozone dose control strategy for O₃/H₂O₂ process was evaluated. Results show that this three-stage process offers high removal of total nitrogen (> 90%), COD (chemical oxygen demand, 60-82%), and micropollutants (atrazine, alachlor, carbamazepine, and bisphenol A, > 96%), satisfying discharge requirements. In the combined post-treatment, ozone dosing for COD removal can be real-time controlled by UVA₂₅₄ reduction monitoring, based on a specific correlation between COD and UVA₂₅₄ changes. On the other hand, O₃/H₂O₂ pre-treatment controlled at a 50% UVA₂₅₄ reduction shows to be the optimal point, when adsorption is designed as the main step for COD removal. Cost analysis shows that post-treatment with low (high) organic load i.e., COD ≤ (≥)540 mg/L, a combination with O₃/H₂O₂ (GAC) as the main step appears to be more cost-effective. Therefore, a dynamic operation strategy in response to the leachate change is recommended.

Combined oxidization and liquid ammonia pretreatment of bamboo of various ages and species for maximizing fermentable sugar release

To determine the potential for improving biomass enzymolysis, a combined oxidization and liquid ammonia pretreatment (OD-LAT) was employed for bamboo. The effects of oxidant, bamboo ages, and species on the pretreatment effectiveness and subsequent enzymolysis were studied. Under the optimal OD-LAT pretreatment and enzymolysis of the B-NA bamboo Neosinocalamus affinis, the glucan and xylan conversion reached 83.85% and 78.66%, respectively, and approximately 59.7-68.5 g of fermentable sugars can be produced per 100 g of dry bamboo, which was an approximately 5-8 fold increase compared with untreated sample. The H₂O₂ loading of 1.0 was the optimal oxidant dosage for the OD-LAT process. The OD-LAT pretreatment was only suitable for bamboo under three-year-old, and it significantly improved the enzymolysis of B-NA and B-BM, while it was limited to B-DO and B-PP. The pretreatment effects of bamboo were not only related to composition but also to the bamboo age, species, macro-structures and micro-structures.